The invention pertains to the field of burglar alarms or overload indicators. Burglar alarms of current usage employ pressure plates, photo electric sensors, ultra-sonic sensors and like devices that can be complicated and expensive.
The present invention provides an alarm device including an alarm switch mounted with respect to a structural component of a building, such as a floor joist, so as to sense deflection of the component as occasioned by the weight of an unwanted intruder walking in the vicinity of the alarm switch.
The alarm device includes a taut horizontal electrically conductive wire strung between two anchoring members on a building component that will deflect when walked upon such as a floor joist or a stair step. An electrical contact is fastened to the building component in close relationship to the wire. When weight is placed above the device by a person walking overhead, there is a deflection of the building component and corresponding deflection of the electrical contact. The wire remains stationary. The deflection occasioned by the weight above the device causes the electrical contact either to come in contact with the wire or to move out of contact with the wire, in either case causing an alarm circuit to be energized.
The alarm device is inexpensive and simple to install and effective in use.